The current flows into what Flickenger calls the “hockey puck of doom”—an end cap of PVC pipe filled with silicone. Inside the gun, a transformer from an old television and additional circuitry repeatedly doubles the current and then pumps it to a capacitor bank. When the six capacitors hold 20,000 volts, the gun starts firing. All that electricity still blew a few pucks, so Flickenger recently tested a mixture of silicone and hexagonal boron nitride that draws away the heat, preserving electrical components.